The instant invention relates to a boat hull construction and more particularly to a novel tunnel-type boat hull construction which has improved high-speed stability and also reduced drag or frictional resistance when it is propelled through the water.
The primary source of resistance to the movement of any boat hull through the water is the frictional resistance which is applied by the water itself to the submerged surfaces of the hull. This phenomenon applies to both displacement-type vessels and planing-type vessels, although in either case the configurations and dimensions of the underwater surfaces of the vessel and the speed at which the vessel is propelled are obviously significant in determining the total frictional resistance which is applied to the vessel by the water during the movement of the vessel. Heretofore it has been known to reduce the frictional resistance or drag which is applied by the water to the submerged surfaces of a boat hull by emitting air in the form of bubbles along the submerged outer surfaces of the hull so that the air bubbles act as a lubricant between the hull surfaces and the water. It has been found that substantial reductions in frictional resistance can be achieved in this manner and that, as a result, substantial improvements in operating efficiency can be realized. In substantially all of the known vessels which have used air as a lubricant, the air has been supplied from forwardly facing ports which have extended upwardly from the deck areas thereof, and in some cases blowers or fans have been utilized for compressing the air to enhance its effectiveness as a lubricant. Most of the known hull constructions which have utilized air for reducing frictional resistance have been constructed with apertures in the submerged surfaces thereof for introducing air bubbles into the water along these surfaces so that when the hull is propelled through the water, the submerged hull surfaces are lubricated by the air bubbles and the frictional resistance to the movement of the hull from the water is substantially reduced. It has been found that the main drawback with respect to the peformance of hulls embodying this feature is that the air bubbles tend to make them somewhat unstable, particularly at high speeds. Other hull constructions which have been adapted to ride on large air pockets have also been generally known, but these hull constructions have also been somewhat unstable at high speeds.
Another factor which is a matter of primary concern in the design of a hull for any water vessel is the stability of the vessel hull at various operating speeds and under various sea conditions. It has been found that multi-hull vessels which comprise a plurality of spaced hull sections having open tunnel areas therebetween are particularly stable at slow and moderate operating speeds. Further, it has been found that one of the most stable multi-hull-type vessels is the tunnel-hull vessel which comprises a pair of spaced hull sections having a single open tunnel area therebetween. However, while multi-hull vessels have proven to be relatively stable at slow and moderate speeds, they have exhibited a tendency to trap large amounts of air under the bow areas thereof when they have been operated at high speeds, and this has often caused the bows of such vessels to be uplifted significantly under these operating conditions. This characteristic has made most multi-hull vessels somewhat unsafe at high speeds, and it has reduced the effectiveness and desirability of multi-hull vessel constructions for high-speed power-boat applications.
This instant invention relates to a novel boat-hull construction which provides both reduced frictional resistance or drag from the water and reduced bow uplift in a multi-hull vessel. Specifically, the boat-hull construction of the instant invention comprises a pair of transversely spaced, longitudinally extending hull sections, and a longitudinally extending connecting section between the hull sections which cooperates therewith to define an open tunnel, and means communicating with the forward portion of the tunnel in an area which is rearwardly spaced from the fore-end of the vessel for withdrawing air from the tunnel and for exiting or emitting the air in submerged areas of the undersides of the hull sections when the hull is underway in a forward direction. Accordingly, when the hull is propelled in a forward direction, air is trapped in the forward portion of the tunnel, and it is compressed by the movement of the vessel and by the configuration of the tunnel. Excess air which might otherwise cause bow uplift effects in the vessel is withdrawn from the forward portion of the tunnel, and this air is emitted along the undersides of the hull sections to provide a lubricating effect. Hence it is seen that the hull construction of the instant invention eliminates the disadvantages of the heretofore-known tunnel-type hull constructions, and it also provides an effective means for compressing air and for utilizing the compressed air for lubricating the submerged surfaces of the hull sections. In the preferred embodiment of the hull construction, air is withdrawn from the tunnel through a downwardly and forwardly facing withdrawal port in the forward portion of the tunnel, and the tunnel is formed to provide a funnel-like entry configuration for the withdrawl port to effect a natural compression of air as it is passed from the fore-end of the hull to the withdrawal port. In addition, in the preferred embodiment, the withdrawal port is spaced upwardly a substantial distance from the waterline of the hull consruction in order to avoid taking substantial quantities of water into the withdrawal port during the operation of the hull under heavy sea conditions. Further, in the preferred embodiment, the hull sections are formed with bottom surfaces which face generally downwardly when the hull is under way, and the air is exited through exit ports which extend substantially transversely across the hull sections so that the air is distributed in substantially uniform sheets of air which extend substantially transversely across the respective bottom surfaces of the hull sections rather than as bubbles, the exit ports preferably being located forward of the center of gravity of the hull construction so that most of the weight of the hull is carried on the air sheets. The exit ports are also preferably dimensioned so that the combined sectional areas thereof are substantially equal to the crosssectional area of the withdrawal port. Further, the main portion of the tunnel, i.e., that portion of the tunnel which is aft of the funnel-like area adjacent the withdrawal port, is preferably formed so that the central portion thereof has a slightly greater vertical height than the fore and aft portions thereof, and so that the aft portion has the smallest vertical height. This provides increased lift in the stern area of the hull construction in order to further minimize air uplift effects on the bow portion of the hull construction, and it also insures that the pressure in the main portion of the tunnel is the greatest in the central portion of the main portion where the vertical height of the tunnel is the greatest. Accordingly, the combined effects of all of these features of the hull construction provide an effective boat hull which can be operated with substantially increased efficiency and which is stable and safe under most sea conditions.
Vessel hull constructions which represent the closest prior art to the instant invention of which the applicant is aware are disclosed in the U.S. patents to Hone Nos. 1,812,265; Higgins 2,234,899; Wilson 3,191,572; Glass 3,547,064; Burg 4,165,703; and Cyr 4,407,215. All of these references teach hull constructions wherein means are provided for introducing air along the submerged surfaces of vessels for lubricating purposes. However, they do not provide means for exiting air in substantially uniform sheets, and they also do not suggest this feature in a tunnel-hull vessel wherein air is withdrawn from the tunnel and exited along the submerged surfaces of the hull sections in order to achieve the unique benefits provided by the hull construction of the instant invention. Hence, for these reasons, as well as for a number of other reasons which will hereinafter be made apparent, all of these references are believed to be of nothing more than general interest.
Accordingly, it is a primary object of the instant invention to provide a boat-hull construction of the type having at least two spaced longitudinally extending hull sections and an open tunnel area therebetween, wherein air is withdrawn from the tunnel and exited along the submerged surfaces of the hull sections to provide reduced frictoinal resistance between the submerged surfaces of the hull sections and the water when the hull construction is under way in a forward direction.
Another object of the instant invention is to provide a tunnel-type boat-hull construction wherein the bow portion of the hull construction is not normally uplifted significantly by air which is captured in the forward portion of the tunnel when the hull construction is operated under high-speed conditions.
A still further object of the instant invention is to provide a hull construction which comprises a pair of spaced hull sections having generally downwardly facing bottom surfaces, wherein air is exited through exit ports to provide substantially uniform continuous sheets of air along the bottom surfaces of the hull sections when the hull construction is under way in a forward direction.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.